# Mssql Server

> Writes, optimizes, and debugs T-SQL queries. Explains SQL Server internals, troubleshoots performance issues, and guides database administration tasks including backup/restore, high availability, security, and index design. Use when the user asks about T-SQL syntax, SQL Server administration, query performance, stored procedures, indexes, locking, transactions, backup/restore, high availability, security, or any MSSQL-related topic — even without saying 'SQL Server' explicitly. Also trigger on terms like SSMS, tempdb, bcp, sqlcmd, MSSQL, sp_executesql, NOLOCK, columnstore, Hekaton, RCSI, param sniffing, or execution plan.

- Skill: `damusix/mssql-server` (Agent Skill, multi-file: 56 files)
- Install (CLI): `npx skillmds@latest add damusix/mssql-server`
- Raw SKILL.md: https://api.skillmd.com/api/skills/damusix/mssql-server/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Data & Analytics
- Author: damusix (https://skillmd.com/u/damusix)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/damusix/mssql-server

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# MSSQL Server Skill

## How to use this skill

1. **Identify the topic** using the routing table below (keyword → file mapping).
2. **Read the relevant reference file(s).** Never answer from memory alone when a reference file covers the topic.
3. **Cross-cutting questions** — identify ALL matching rows and read each file. Check "See Also" sections for additional files.
4. **Ambiguous keywords** — read the "Disambiguation" column. When in doubt, load both files.
5. **Response format:** Lead with code/pattern, follow with caveats in admonition blocks, end with source links.

## Quick Examples

    -- Basic filtered query with pagination
    SELECT CustomerName, Email
    FROM Customer
    WHERE Status = 'Active'
    ORDER BY CustomerName
    OFFSET 0 ROWS FETCH NEXT 25 ROWS ONLY;

    -- Create a covering index
    CREATE NONCLUSTERED INDEX IX_Customer_Status
    ON Customer(Status) INCLUDE (CustomerName, Email);

---

## Routing Table


| Keywords / Triggers | File | Scope | Disambiguation |
|---|---|---|---|
| CREATE TABLE, ALTER TABLE, DROP, schema, sequence, synonym, computed column | `references/01-syntax-ddl.md` | DDL syntax reference | |
| SELECT, JOIN, subquery, UNION, INTERSECT, EXCEPT, window function, PIVOT, UNPIVOT, APPLY, OFFSET FETCH, pagination | `references/02-syntax-dql.md` | DQL / query syntax | |
| INSERT, UPDATE, DELETE, MERGE, OUTPUT clause, upsert | `references/03-syntax-dml.md` | DML syntax & patterns | |
| CTE, WITH, recursive CTE, anchor member, MAXRECURSION | `references/04-ctes.md` | CTEs (recursive & non-recursive) | |
| VIEW, indexed view, SCHEMABINDING, partitioned view, WITH CHECK OPTION | `references/05-views.md` | Views | |
| stored procedure, param sniffing, TVP, output param, EXECUTE AS user, impersonation, security context | `references/06-stored-procedures.md` | Stored procedures | **OPTION RECOMPILE**: here for proc-level usage; see also 32 for query-level hint. **EXECUTE AS**: here for proc context; see also 15 for server/db principals |
| function, scalar UDF, inline TVF, multi-statement TVF, determinism, UDF inlining | `references/07-functions.md` | User-defined functions | |
| index, clustered, nonclustered, covering index, include columns, fill factor, fragmentation, heap, forwarded record, rebuild, reorganize, B-tree structure | `references/08-indexes.md` | Index design & maintenance | **missing index**: here for DMV queries and index design; see also 32 for broader perf diagnostics |
| columnstore, delta store, rowgroup, batch mode, tuple mover, segment elimination | `references/09-columnstore-indexes.md` | Columnstore indexes | |
| partition, partition function, partition scheme, partition switching, sliding window, STATISTICS_INCREMENTAL | `references/10-partitioning.md` | Table partitioning | |
| user-defined type, CLR type, table type, alias type, spatial, geometry, geography, sparse column | `references/11-custom-data-types.md` | Custom data types | |
| CHECK constraint, DEFAULT constraint, UNIQUE constraint, foreign key, cascade, referential integrity, functional constraint, cross-database constraint, cross-schema, computed column index | `references/12-custom-defaults-rules.md` | Constraints & defaults | |
| transaction, isolation level, SNAPSHOT, RCSI, READ_COMMITTED_SNAPSHOT, ALLOW_SNAPSHOT_ISOLATION, MVCC, row versioning, lock escalation, lock hint, NOLOCK, UPDLOCK, ROWLOCK | `references/13-transactions-locking.md` | Transactions & locking | **deadlock**: here for theory, prevention, lock mechanics; see also 33 for XE deadlock graph capture. **wait stats**: here for lock-related waits; see also 32 for full wait stats diagnostics |
| TRY CATCH, THROW, RAISERROR, error handling, savepoint, @@TRANCOUNT, XACT_ABORT | `references/14-error-handling.md` | Error handling | |
| login, user, role, server principal, database principal, GRANT, DENY, REVOKE, permission, ownership chaining, application role | `references/15-principals-permissions.md` | Principals & permissions | **EXECUTE AS**: here for principal impersonation; see also 06 for proc-level EXECUTE AS |
| RLS, row-level security, dynamic data masking, TDE, Always Encrypted, column encryption, certificate, DDM, encryption algorithm, AES, RSA, CEK, CMK, key rotation, HSM | `references/16-security-encryption.md` | Security & encryption | |
| temporal table, system-versioned, AS OF, time travel, FOR SYSTEM_TIME, retention policy | `references/17-temporal-tables.md` | Temporal tables | |
| In-Memory OLTP, Hekaton, memory-optimized table, natively compiled, hash index, range index, durability | `references/18-in-memory-oltp.md` | In-Memory OLTP | |
| JSON, XML, FOR JSON, FOR XML, OPENJSON, JSON_VALUE, JSON_QUERY, JSON_MODIFY, XQuery, XML index | `references/19-json-xml.md` | JSON & XML | |
| full-text search, FTS, CONTAINS, FREETEXT, CONTAINSTABLE, FREETEXTTABLE, semantic search, stopword, thesaurus | `references/20-full-text-search.md` | Full-text & semantic search | |
| graph table, node table, edge table, MATCH, SHORTEST_PATH, multi-hop, graph traversal | `references/21-graph-tables.md` | Graph tables | |
| ledger table, append-only ledger, updatable ledger, digest, ledger verification, blockchain | `references/22-ledger-tables.md` | Ledger tables | |
| dynamic SQL, sp_executesql, SQL injection, parameterized query, dynamic WHERE, EXEC | `references/23-dynamic-sql.md` | Dynamic SQL | |
| string function, date function, math function, STRING_AGG, CONCAT_WS, FORMAT, DATEADD, DATEDIFF, AT TIME ZONE, datetime2, datetimeoffset, TRIM, TRANSLATE | `references/24-string-date-math-functions.md` | Built-in functions reference | |
| NULL, ISNULL, COALESCE, NULLIF, three-valued logic, IS DISTINCT FROM, nullable index | `references/25-null-handling.md` | NULL handling | |
| collation, case-sensitive, accent-sensitive, COLLATE clause, collation conflict, Latin1_General, BIN2 | `references/26-collation.md` | Collation | |
| cursor, FAST_FORWARD, KEYSET, STATIC, DYNAMIC, FORWARD_ONLY, cursor anti-pattern | `references/27-cursors.md` | Cursors | |
| statistics, auto-update, ascending key, histogram, DBCC SHOW_STATISTICS, UPDATE STATISTICS, filtered statistics | `references/28-statistics.md` | Statistics | |
| execution plan, SHOWPLAN, STATISTICS IO, STATISTICS TIME, Index Seek, Key Lookup, Hash Join, Nested Loop, cardinality, plan warning, implicit conversion | `references/29-query-plans.md` | Query plans | |
| Query Store, regressed query, forced plan, PSPO, parameter-sensitive plan, CE feedback | `references/30-query-store.md` | Query Store | **wait stats**: here for QS-integrated wait stats; see also 32 for server-level wait stats |
| IQP, Intelligent Query Processing, memory grant feedback, batch mode on rowstore, interleaved execution, DOP feedback, table variable deferred compilation, approximate count | `references/31-intelligent-query-processing.md` | Intelligent Query Processing | |
| wait stats, missing index DMV, plan cache, OPTION RECOMPILE, MAXDOP hint, sp_Blitz, sp_BlitzCache, sp_BlitzFirst, sp_BlitzIndex, FORCESEEK, FORCESCAN | `references/32-performance-diagnostics.md` | Performance diagnostics | **OPTION RECOMPILE**: here for query hint usage; see also 06 for proc-level param sniffing. **missing index**: here for perf triage; see also 08 for index design decisions |
| Extended Events, XE session, deadlock graph, blocking detection, ring buffer, event file, sys.dm_xe | `references/33-extended-events.md` | Extended Events | **deadlock graph**: here for XE capture mechanics; see also 13 for deadlock theory and prevention |
| tempdb, TF 1117, TF 1118, GAM, SGAM, PFS, allocation latch, temp table, table variable, version store | `references/34-tempdb.md` | tempdb | |
| DBCC, CHECKDB, FREEPROCCACHE, DROPCLEANBUFFERS, SHRINKFILE, SHRINKDATABASE, UPDATEUSAGE, INPUTBUFFER, OPENTRAN | `references/35-dbcc-commands.md` | DBCC commands | |
| data compression, ROW compression, PAGE compression, COLUMNSTORE compression, sp_estimate_data_compression_savings | `references/36-data-compression.md` | Data compression | |
| CDC, Change Data Capture, Change Tracking, CT, ETL, cdc.fn_cdc_get_all_changes, CHANGETABLE | `references/37-change-tracking-cdc.md` | Change Tracking & CDC | |
| SQL Server Audit, SERVER AUDIT, audit specification, compliance, SOX, HIPAA, PCI-DSS, audit log | `references/38-auditing.md` | Auditing | |
| trigger, DML trigger, DDL trigger, logon trigger, AFTER, INSTEAD OF, inserted, deleted, COLUMNS_UPDATED | `references/39-triggers.md` | Triggers | |
| Service Broker, SSB, queue, SEND, RECEIVE, dialog conversation, activation, message type, contract, pub/sub | `references/40-service-broker-queuing.md` | Service Broker & queuing | |
| replication, snapshot replication, transactional replication, merge replication, publisher, distributor, subscriber, replication agent | `references/41-replication.md` | Replication | |
| database snapshot, AS SNAPSHOT OF, sparse file, REVERT, consistent read | `references/42-database-snapshots.md` | Database snapshots | |
| Always On, Availability Group, AG, listener, readable secondary, quorum, distributed AG, contained AG, log shipping, FCI, failover cluster | `references/43-high-availability.md` | High availability | |
| BACKUP, RESTORE, full backup, differential, log backup, tail log, point-in-time restore, NORECOVERY, STANDBY, S3 backup, backup encryption | `references/44-backup-restore.md` | Backup & restore | |
| linked server, four-part name, OPENQUERY, OPENDATASOURCE, distributed transaction, DTC | `references/45-linked-servers.md` | Linked servers | |
| PolyBase, external table, external data source, OPENROWSET, S3, Azure Blob, Hadoop, predicate pushdown | `references/46-polybase-external-tables.md` | PolyBase & external tables | |
| sqlcmd, bcp, sqlpackage, mssql-cli, BULK INSERT, OPENROWSET BULK, format file, dacpac, bacpac, PowerShell SQLServer | `references/47-cli-bulk-operations.md` | CLI & bulk operations | |
| Database Mail, sp_send_dbmail, mail profile, mail account, HTML mail, Agent alert notification | `references/48-database-mail.md` | Database Mail | |
| sp_configure, max server memory, MAXDOP, cost threshold, Resource Governor, trace flag, NUMA | `references/49-configuration-tuning.md` | Configuration & tuning | **MAXDOP**: here for server config; see also 32 for MAXDOP query hint |
| SQL Server Agent, job, job step, schedule, alert, operator, proxy, msdb, multi-server | `references/50-sql-server-agent.md` | SQL Server Agent | |
| SQL Server 2022, ledger 2022, S3 backup 2022, contained AG 2022, IS_DISTINCT_FROM, GREATEST, LEAST, XML compression | `references/51-2022-features.md` | SQL Server 2022 features | |
| SQL Server 2025, vector search, VECTOR type, vector index, AI features, 2025 T-SQL | `references/52-2025-features.md` | SQL Server 2025 features | |
| compatibility level, CE version, cardinality estimator, deprecated feature, upgrade, migration, contained database | `references/53-migration-compatibility.md` | Migration & compatibility | |
| SQL Server on Linux, Docker, mssql-conf, container, Pacemaker, mssql-tools, Linux limitations | `references/54-linux-containers.md` | Linux & containers | |